The present invention relates to a method and apparatus for inputting coordinates. More specifically, this invention relates to a method and apparatus for optically inputting coordinates.
At present, an apparatus which can detect a position on the surface of a panel (e.g. a touch panel) that has been specified by touching with a finger or a pen, and inputs the detected coordinates are input into a computer or the like is known. An example of such a coordinates inputting apparatus has been disclosed, for instance, in Japanese Patent Laid-Open Publication No. HEI 9-91094. In this coordinates inputting apparatus, one light scanner is provided at two of the four corners of the touch panel. Each light scanner outputs a light flux which is parallel to a surface of the touch panel. A receiver receives the light flux.
When the user touches the touch panel with his (her) finger or pen, the light flux output from the light scanners is cut and the light flux is not received by the receiver. Coordinates of the position where the finger or the pen touches the touch panel are calculated from the position on the receiver where the light flux is not received. The calculated coordinates are then input into an external device. This type of coordinates inputting apparatus is sometimes called as an optical coordinates inputting apparatus, and it is widely used because of its is relatively simple configuration.
With the conventional optical coordinates inputting apparatus, however, a dark area where a light flux does not reach (described hereinafter as a gap between the light flux and the touch panel) is generated between the light flux and the touch panel, and sometimes coordinate values can not be detected in this area. This phenomenon occurs due to incorrect adjustment of the optical system that includes the light scanner, or because a portion of a light flux on the surface of the touch panel is cut due to a member which is provided to support the touch panel.
When a position in the vertical direction (in the depth direction) of a shielding object (finger or pen) matter against the touch panel is to be detected, the gap between the light flux and the touch panel surface may cause such problems as described below. That is, when the touch panel also has a function of displaying data on a display screen, a double click is detected as one click. Further, even though the pen (or finger) is separated from the surface of the touch panel cutting of the light flux apparently continues and a character is displayed continuously. Such problems become prominent as the gap between the light flux and the touch panel becomes wider. This causes a drop in the precision in detection of coordinates by the coordinates inputting apparatus and to detect erroneous coordinates.
The gap between the light flux and the touch panel surface can be made narrower by adjusting the optical system (for example, adjusting the height or inclination of the light source). However, a relatively longer time, skill and expertise are is required for such an adjustment. Thus, narrowing of the gap between the light flux and the touch panel surface by adjusting the optical system is relatively difficult.
It is an object of the present invention to provide a coordinates inputting apparatus which enables easy reduction of a gap between the light flux and the touch panel surface and further insures high precision in detection of the coordinates.
The coordinates inputting apparatus according to this invention comprises a plurality of light sources provided on different positions on the touch panel, reflection members which recursively reflect the light, and light-receiving sections which receive the light and detect whether the light was cut at certain position on the touch panel. The light sources output the light at certain angle with the touch panel surface (that is, the light is not parallel to the touch panel). The light output from the light source is reflected by the touch panel, then recursively reflected by the reflection members, once more reflected by the touch panel and finally enters into light-receiving sections. Thus, a portion of a light flux is not shielded by a member which supports a touch panel. Further, generation of a gap between the light flux output from the light sources and the touch panel surface can be prevented without minutely adjusting the optical system.
Further, the light sources output light fluxes toward the center of the touch panel. Therefore, the light can be efficiently delivered onto the whole surface of the touch panel. Accordingly, the whole surface of the touch panel can be used as a field for inputting the coordinates.
Further, the light sources are held at specified positions and output light fluxes toward the center of the touch panel. Thus, the light sources can be installed at a required position under stable conditions, and once adjusted, the light source section can be fixed in the stable state.
Further, the angle of incidence of the light flux output from the light sources onto the touch panel is less than the angle at which total reflection from the touch panel will take place. Therefore, the light flux falling on the touch panel can accurately be reflected, and a reflected light can be generated efficiently.
Further, the light sources are located such positions that the angle of incidence of the light flux output from the light sources onto the touch panel is less than the angle at which total reflection from the touch panel will take place. Thus, the light source section can be fixed in the stable state in which the light flux falling on the touch panel can accurately be reflected, and a reflected light can be generated efficiently.
Further, the light sources are two in number and each light source is positioned at a different portion on the flat surface. Because only the minimum required number of light sources are provided, a low cost coordinates inputting apparatus can be realized.
Further, one of the light source and one of said light-receiving section are integrated into one optical unit, and all of the light sources are arranged substantially in one plane and, each of the light source outputs a light flux spreading in a fan form from with the position at which the light source is located as the center. Accordingly, precision in assembly of light sources and the light-receiving sections with respect to the touch panel can be improved, and once adjusted, relative positions of the light sources and light-receiving sections are not displaced even when an external force is loaded to the optical system.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.